Manufacturing smaller IC packages results in a final end product proportionally reduced in size. However, in today's integrated circuit (IC) packages, microelectromechanical systems (MEMS) devices (such as a SAW filter) are conventionally mounted on top of a packaging substrate supporting the IC. In this case, the MEMS devices occupy area in the package that may otherwise be used for additional integrated circuitry or eliminated to reduce IC package size. Alternatively the MEMS device may be mounted in a package separate from the IC. In this case, the overall footprint of the system is still increased.
Stacking a MEMS device on an IC reduces the footprint of the IC package but increases the height and adds challenges to IC packaging. Even if height is not of concern, stacking the MEMS device on the IC may prevent stacking another IC. Another disadvantage of stacking the MEMS device on top of an IC is increased stress on the MEMS device resulting from over-mold, which is part of the packaging process.
Although dies have been embedded in packaging substrates to reduce the overall size, MEMS devices have not been considered as candidates for embedding. MEMS devices include many mechanical structures that are sensitive to stress. High stresses created by the manufacturing process for embedding prevents MEMS devices from being embedded. Additionally, during operation environmental factors (e.g., temperature) would add stress to the embedded MEMS device. For example, stresses from the bottom and top surfaces of the package would be transferred to the MEMS device, reducing performance or otherwise impacting operation of the MEMS device.
Thus, it would be desirable to reduce the size of packages including MEMS devices without overly stressing the MEMS device.